A cylinder lock actuable by a round key shaft is conventionally provided with a key engaging means at the inner end of its cylinder to engage with a notch formed at the end of the key shaft such that the cylinder can be caused to turn to lock or unlock the lock device when the key is rotated. With such a construction, the key's use may be inconvenient, especially in a dim or dark place, as the user has to insert the key into the keyhole at a predetermined orientation to cause the aforementioned operations to succeed.
Furthermore, although the security of a cylinder lock can be increased by adding a number of tumbler assemblies, it increases the size, cost and complexity of the lock, thus making the same not commercially economical.
In view of the aforesaid drawbacks, one object of this invention is to provide a cylinder lock without a key engaging means which can be actuated by a round key shaft axially inserted into the keyhole at a random orientation.
Another object of this invention is to provide a cylinder lock which is simple in construction, but still pick-resistant.